Influences Of Madden-julian Oscillation In The Formation And Development Of Tropical Cyclones In The Western North Pacific During Autumn And Winter

Based on the tropical cyclones formed in the western north Pacific during 1984-2013 autumn and winter,using the NCEP/NCAR Daily Reanalyze Index,OLR,Real-Time Multivariate MJO Index and JTWC best track,the influence of Madden-Julian Oscillation in the formation and development to tropical cyclone formed in western north Pacific during autumn and winter are discussed by the filter technology and the composite method.There are less than one-tenth MJO activities active in phase5 during the autumn and winter,while the formation of nearly half of the tropical cyclones is associated to phase5 of MJO,and the formation of more than half of the super typhoons is related to phsae5 of MJO.The results of filtering and composite analysis show that MJO provides a more favorable large-scale environmental condition for the development of tropical cyclones in the Northwest Pacific.By the influence of MJO,the large-scale environmental low-level cyclone convergence and the superior anticyclonic divergence in the tropical cyclone formation area are more significant.Further analysis shows that the location of the tropical cyclone relative to the active center of the MJO can be nearly as far away.The eastward MJO not only contributes directly to the formation of tropical cyclones through its own favorable conditions,but also affects the formation and development of tropical cyclones by triggering the quasi-biweekly oscillation which propagate westward and the synoptic-scale wave train from east to west.